REINFORCEMENT CONTEXT AND PACEMAKER RATE IN THE BEHAVIORAL-THEORY OF TIMING

In the present experiment, an attempt was made to extend the base of e vidence for the assumption of the behavioral theory of timing that pac emaker rate is determined by reinforcement rate. Pigeons discriminated the first half from the second half of a 50-sec trial in a free-opera nt psychophysical procedure. Left-key responding was reinforced at var iable intervals during the first 25sec, and right-key responding was r einforced at variable interval during the second 25 sec. The rate of ' 'extraneous'' reinforcers delivered at variable intervals following re sponses to a center key was manipulated independently of performance i n the temporal discrimination. Quantitative estimates of pacemaker rat e were not directly proportional to extraneous rate of reinforcement, whether extraneous reinforcers were available during the intertrial in terval, the entire session, or the trial only. Instead, estimates of p acemaker rate were inversely related to the rate of extraneous reinfor cement, which suggests that pacemaker rate is determined by the ratio of the rate of reinforcement for the timing response relative to other sources of reinforcement.